A system in which the relative distance between a gantry device and a measuring point located outside the gantry device is determined is described, for example, in the datasheet from Symeo in relation to the sensor system LPR-1 DX, wherein the datasheet can be found online at    http://www.symeo.com/Deutsch/Downloads/Download-Symeo-Datenblaetter.html. The designation LPR stands for Local Positioning Radar. The radar sensor system LPR-1 DX is based on the principle of transit time measurement of radio waves and can serve to determine distances, for example, relative distances, between two objects. The radar senor system is a contactless system for measuring distances. For example, in the specified datasheet there is a graphic illustration of a gantry crane, for example, in container ports. A radar sensor can be mounted on the gantry crane. A crane bridge can be arranged in such a way that the crane bridge can move in relation to the gantry crane and a radar sensor. The two radar sensors can determine the distance from the respective other sensor, for example, the distance between the gantry crane and the crane bridge can be determined in a redundant fashion. The datasheet proposes use of the radar sensor system LPR-1 DX to help avoid collisions and prevent the gantry crane and crane bridge moving unacceptably close to one another.
Furthermore, on the Internet page www.symeo.com/Deutsch/Schuettgut, the page recommends that the LPR sensors can be used to locate and measure movement when handling bulk material. Bulk material can be understood below to mean loose material which can be acquired by removal processes, and is then intermediately stored at what can be referred to as bulk material storage spaces, these materials being, for example, coal, ore, sand or gravel. The transportation of the bulk material to the storage location and the storage of the bulk material in heaps of bulk material, and the removal from storage and transportation away can be performed by what can be referred to as storage space devices, such as, for example, cranes, excavators, spreaders and conveyor belts. Symeo determines the movements of the storage space devices at such bulk material storage spaces by means of linear distance measurement using radar sensors, or an absolute position determining process by means of a combination of GPS with radar sensors. The combination of GPS with radar sensors can be used in the case of automated machine movements to help avoid collisions between the storage space devices.
In the dissertation by Sergiy A. Kaverynskyy, “Zustandsorientierte Instandhaltung und Teleservice für Schüttgut-Materialflusssysteme” [State-oriented maintenance and teleservice for bulk material flow systems], ISBN-10: 3930385422, ISBN-13: 978-3930385423, a coal-handling system is described, which can continuously supply a coal power station. The coal can be intermediately stored at a bulk material storage space before being transported on in the direction of the power station, and can be mixed at the bulk material storage space such that the ash content and the heating value of the coal introduced into the power station corresponds to predefined values. The bulk material storage space can also be referred to as a coal mixing and storage yard. For example, two storage space device types can be active at the coal mixing and storage yard. A spreader for piling up one or more heaps of coal and a gantry scraper for removing the coal from storage, for example for conveying the coal from the coal heap to a conveyor belt. As described, the spreader and the gantry scraper travel on rails, which can be laid parallel to the heap of coal. The gantry scraper can have for this purpose, geared motors as running gear drive in the running gear of its two leg elements and associated foot elements, for example, combinations of the electric motor and gear mechanisms. Absolute rotary encoders can be used to determine the position of the gantry scraper, and the position can be in turn used to avoid collisions and to detect skewed running. Skewed running can be understood to mean that the two sides or legs of the gantry move at different distances along the rails, with the result that stresses can occur in the gantry structure and there can be an undesired application of force into the tracks of the rail lines. In order to avoid these stresses when a predefined deviation from the straight running is reached the speed of one of the running gear drives is changed in the downward or upward directions by negative or positive set point value implementation until the straight running can be restored.